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Which of these is not required for electrophilic catalysis?

(a) Mg^2+

(b) Zn^2+

(c) Mn^2+

(d) Ser 195

This question was addressed to me in class test.

My question comes from Enzyme Kinetics topic in chapter Enzyme Kinetics of Enzyme Technology

1 Answer

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The correct option is (a) Mg^2+

Easy explanation: Electrophilic catalysis involves covalent intermediate transition state formation between the cationic electrophilic group in the enzyme and the electron rich portion of the substrate. Most of the amino-acid side chains in the active site don’t act as an efficient electrophile. So, most of the enzymes require metal ions such as Mg^2+, Zn^2+, Mn^2+, etc., as an electron deficient electrophile for optimum catalysis. Ser 195 is an amino-acid in the active site chymotrypsin which hydrolyses peptides.

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